Packaged antenna and method for producing same

ABSTRACT

Electronic apparatus having an antenna chip with a substrate and an antenna structure, and a method of producing the same. The antenna chip is integrated or packaged in a package having a chip mounting surface for mounting the antenna chip, and an encapsulating material. The encapsulating material typically is a plastic mold used in the industrial packaging of integrated circuits. Between the antenna structure and the chip mounting surface, a first void is disposed in the substrate.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/746,480, which was filed May 9, 2007. This application isincorporated herein by reference in its entirety.

BACKGROUND

The present invention generally relates to apparatus and methods forpackaging antenna devices and, in particular, apparatus and methods forpackaging antenna chips to thereby form compact integrated radar, radioor wireless communications systems for high frequency applications.

Antenna structures are used in a variety of applications. Communicationdevices are equipped with antennas to enable wireless communicationbetween devices in network systems such as wireless PAN (personal areanetwork), wireless LAN (local area network), wireless WAN (wide areanetwork), cellular network systems, and other types of radio systems.

Further applications include radar sensors, for example in the frequencyrange between 76 GHz and 81 GHz, which have gained importance in avariety of technical fields like automotive technology (collisionavoidance, pre crash safety, etc.), motion sensoring in households andthe like.

With conventional radar, radio or wireless communications systems,discrete components are individually encapsulated or individuallymounted with low integration levels on printed circuit boards, packagesor substrates. This usually causes significant losses at those highoperating frequencies. At the same time, the miniaturization of thesystems becomes more important, as robustness and reliability arerequired in the respective environments. Accordingly, there is a desireto package these electronic devices more densely. This, however, poses anumber of challenges to designers, as high frequency appliances have tobe integrated in hermetically closed packages while at the same timeminimizing degrading effects on the emission characteristics andefficiency of the applied antennas.

Hence, there is a need for a technology to integrate antenna structuresinto a package and to improve the emission behavior of a radar antennastructures which are encapsulated in a package.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the invention will be described below with reference toexemplary embodiments which are shown in the appended figures. However,the invention is not restricted to the specifically described exemplaryembodiments but rather may be modified and varied in a suitable manner.It is within the scope of the invention to combine individual featuresand combinations of features of one exemplary embodiment with featuresand combinations of features of another exemplary embodiment.

FIG. 1 shows a sectional view of a first embodiment of the presentinvention;

FIG. 2 shows a sectional top view of a first embodiment of the presentinvention.

FIG. 3 shows a sectional view of another embodiment of the presentinvention comprising a circuit;

FIG. 4 shows a circuit diagram showing a part of a circuit according toan embodiment of the present invention;

FIG. 5 shows a sectional view of another embodiment of the presentinvention;

FIG. 6 shows a sectional view of another embodiment of the presentinvention;

FIG. 7 shows a sectional view of further embodiment of the presentinvention;

FIG. 8 shows a sectional view of still another embodiment of the presentinvention;

FIG. 9 shows a typical, simplified block diagram of a monostatic FMCWradar sensor used for the present invention;

FIG. 10 shows a typical, simplified block diagram of a data transmitterused for the present invention;

FIG. 11 shows a typical, simplified block diagram of a data receiverused for the present invention;

FIG. 12 shows a sectional view of further embodiment of the presentinvention; and

FIG. 13 shows a sectional top view of the embodiment shown in FIG. 12.

DETAILED DESCRIPTION OF THE INVENTION

A first aspect of the present invention provides an electronic apparatuswhich includes an antenna chip or a chip that accommodates an antenna aswell as other active and passive circuitries. The chip includes asubstrate and an antenna structure. The apparatus further includes apackage having a chip mounting surface and an encapsulating material. Afirst void is arranged in the substrate in the vicinity of the antennastructure.

In a second aspect of the present invention, an electronic apparatus isprovided, which includes an antenna chip having a substrate and anantenna structure with optional active/passive circuitries. Theapparatus further includes a package which includes a chip mountingsurface and an encapsulating material, and a cap covering the antennastructure. A second void is arranged between the antenna structure andthe cap.

A third aspect of the present invention provides a method of producingan electronic apparatus comprising an antenna chip and a package. Themethod includes the steps of providing a substrate, producing an antennastructure on an upper face of the substrate, producing a first void inthe substrate, disposing the substrate on a chip mounting surface of thepackage, and providing a encapsulating material to seal the package.

In a fourth aspect of the present invention, there is provided a methodof producing an electronic apparatus comprising an antenna chip and apackage. The method includes the steps of providing a substrate,producing an antenna structure on an upper face of the substrate,disposing a cap on the upper face of the substrate covering the antennastructure, disposing the substrate on a chip mounting surface of thepackage, and providing a encapsulating material to seal the package.

As a result of the use of an electronic apparatus with an antennastructure having one or more voids disposed in its vicinity, theemission characteristics of the antenna is improved.

In order to simplify understanding of the description, identicalreference numbers are used below when identical elements which are usedtogether in the figures are involved. Elements in one embodiment mayalso be used in another embodiment without this being individuallymentioned in each case.

FIG. 1 shows a first embodiment of the present invention. FIG. 1 showsan electronic apparatus 10 having an antenna chip 20 with a substrate 25and an antenna structure 30. The antenna chip 20 is integrated orpackaged in a package 40 having a conducting chip mounting surface 50for mounting the antenna chip, and an encapsulating material 60. Theencapsulating material may be, but is not limited to a typical plasticmold used in the industrial packaging of integrated circuits. Betweenthe antenna structure 30 and the chip mounting surface 50, a first void100 is arranged in the substrate 25 in the vicinity of the antennastructure 30. The substrate height may be adjusted to the individualoperating wavelength. Preferably, substrate height is a quarter of theoperating wavelength to support radiation in the direction of the frontside of the antenna chip.

The antenna structure 30 may be formed of any suitable material orcombination of materials including, for example, dielectric or isolativematerials such as fused silica (SiO₂), silicon nitride, imides, pcb assupporting and/or embedding material and conducting materials likealuminium, copper, gold, titanium, tantalum and others or alloys ofthose conductors as active antenna materials. The antenna substrate 25may be formed of semiconductor materials such as silicon, GaAs, InP, orGaN, especially if further circuit components are to be integrated intothe antenna chip 20. Other types of substrate like glass, polystyrene,ceramics, Teflon® based materials, FR4 or similar materials are alsoincluded.

FIG. 2 shows a top sectional view of the above described embodiment ofthe present invention. The shape of the antenna structure 30 should beregarded as an example and as non-limiting. The antenna structure 30 maytake the form of a variety of antenna types like Patch, Folded Dipole,Butterfly, Leaky wave, etc.

The present invention thus relates to the practice of disposing at leastone void adjacent to an antenna structure. This significantly improvesthe emission and/or receiving characteristics of the antenna and thusallows reducing the applied power to achieve a certain radiated power orin case of receiving allows for a improved signal to noise figure. Atthe same time, homogeneity of the field distant from the antenna isimproved. Furthermore, the electronic apparatus 10 allows for a densepackage of the antenna structure which leads to the furtherminiaturization of the overall systems which use the antenna structure.Despite the dense package the emission and/or receiving characteristicsof the antenna is improved and the mechanical robustness and reliabilityof the antenna structure can be guaranteed.

In an embodiment of the invention, the first void 100 is produced byetching the substrate 25 under the antenna structure 30. In case ofsilicon substrates the first void is preferably formed by a bulk etchingprocess from a bottom surface of the substrate opposite to the antennastructure. The silicon bulk etching process can be performed by using aTMAH of KOH wet etch process or a plasma etching to etch off the bulksilicon.

The first void 100 typically has a size similar or larger to that of theantenna structure 30. Preferably, when the shape of the first void isprojected vertically on the antenna structure, it is about 1/10 largerthan the largest dimension of the antenna. Voids which are significantlylarger than the antenna structure may also be used. The void may also besegmented, e.g. to improve mechanical stability of the assembly.

In a further embodiment of the invention shown in FIG. 5, the electronicapparatus further comprises a second void 110 disposed between theantenna structure 30 and the encapsulating material 60. The second voidserves to improve the emission characteristics of the antenna, aswithout a void the encapsulating material or mold would be in directcontact with the antenna structure, which might worsen theemission/receiving characteristics.

There are a variety of options to realize a second void. In anembodiment of the present invention, an additional cap 70 is placed onthe antenna structure 30 before the packaging of the apparatus, i.e.prior to the application of the encapsulating material 60 or mold mass.A suitable cap for this purpose is for example a SU8 frame. In a furtherembodiment of the present invention, the second void is realized byusing the encapsulation material in the form of an encapsulating lid 65(FIG. 7) that is not in direct contact with the antenna chip 30.

In another embodiment of the invention shown in FIG. 3, the electronicapparatus further comprises a high frequency circuit chip 120 mounted tothe chip mounting surface 50 of the package 40. The circuit serves toprovide signals to the antenna structure 30 and to receive signals fromit. It may comprise further electronic parts and components necessary torealize a radar, radio or wireless communication system in combinationwith the antenna structure, i.e. oscillators, mixers, frequencydividers, etc.

In the embodiment shown in FIG. 3 the high frequency circuit chip 120and the antenna chip 30 are connected via wirebonds interconnects 125.In a further embodiment of the present invention the high frequencycircuit chip 120 and the antenna chip 30 are connected via bumps in aflip chip configuration. For example the filter circuit chip 120 mightbe placed upside down on top of the antenna chip 20 outside the area ofthe antenna structure 30. A combination of the antenna structure withactive circuit blocks on one common chip shall be another embodiment.

FIG. 4 shows a circuit diagram of the receiver part of a communicationcircuit according to an embodiment of the invention. This circuit shouldbe regarded as a non-limiting example. It comprises a Low-Noise-Amlifier(LNA) 200, a first mixer 210, an intermediate frequency amplifier 220, avoltage controlled oscillator 230, amplifiers 240, 250, 260, 270, 280, afirst frequency divider 310, a second frequency divider 320, and twosecond mixers 330, 340. The circuit is connected to an external phaselocked loop 350.

The circuit 120 may be accompanied by an additional resonator chip 130to filter the received signals, which can for example be a bulk acousticwave filter or a DR filter etc.

In order to achieve a high level of integration of the electroniccomponents on circuit 120, it is preferably, but not necessarilyrealized in SiGe-technology.

Furthermore, the present invention may also be employed in connectionwith radar sensors. Due to the small wavelengths occurring in the targetoperation frequency range of about 76 to 81 GHz, very small antennas canbe used in the present invention. A typical antenna area is smaller than2 mm².

In a further embodiment of the invention, the circuit 120 and theantenna chip 20 are integrated on a single chip using a singlesubstrate, which can contribute to further miniaturize the electronicapparatus and to reduce production costs. However, depending ontechnical requirements, chosen operating parameters and the like, it canbe advantageous to employ separate chips for the antenna and the circuitas described above.

FIG. 9 shows a radar transmitting and receiving circuit integrated withantenna within one common Si substrate. The height and caps of the voidsabove and/or below the antenna can be adjusted to allow for preferredradiation and/or reception to the top surface or bottom surface of thestructure (FIG. 12, 13). In case of radiation/reception to the bottomopenings in the chip carrier can be provided.

The antenna structure 30 of the present invention can be used to work asa radar antenna according to a variety of principles, which arecontinuous wave, continuous wave/Doppler, Frequency Modulated ContinuousWave (FMCW), and pulsed mode. Of those, continuous wave and continuouswave/Doppler are most common. The FMCW mode is suitable to detect thedistance to a target object, whereas pulsed mode may be preferred ifenergy consumption of the sensor should be minimized.

FIG. 6 shows another embodiment of the present invention. FIG. 6 showsan electronic apparatus 10 having an antenna chip 20 with a substrate 25and an antenna structure 30. The antenna chip 20 is integrated orpackaged in a package 40 having a chip mounting surface 50 for mountingthe antenna chip, and an encapsulating material 60. The encapsulatingmaterial may be, but is not limited to a typical plastic mold compoundused in the industrial packaging of integrated circuits. Suitable moldcompounds are for example CEL 9240 HF, EME G770I, EME G760D-F, KMC2520L.

As can be seen from FIG. 7 the encapsulating material may, as analternative, also take the form of a lid 65, preferably a metal lid,having an opening 66 for radiating the signal power. As a furtheralternative the lid 65 does not comprise an opening 66 but, instead,chip mounting surface 50 comprises an opening adjacent to the void 100in the antenna substrate 25 similar to the embodiment of the presentinvention shown in FIG. 12. Thereby, the distance between the antennastructure and the lid is preferably a quarter of the operatingwavelength to support radiation in the direction of the back side of theantenna chip.

In case the encapsulating material is plastic mold compound (FIG. 6) acap 70 is covering the antenna structure 30. A second void is disposedbetween the antenna structure 30 and the cap 70. The second void servesto improve the emission characteristics of the antenna, as without avoid the mold material 60 would be in direct contact with the antennastructure, which might worsen the emission characteristics. Thisembodiment can be combined with other features according to the presentinvention as hereinbefore described with respect to other embodiments.

Due to the small size of the antenna structure 30, it is possible todesign the electronic apparatus of the present invention with a verysmall volume of only a few mm³. A preferred package for small electronicsystems is the Thin Small Leadless Package (TSLP). Accordingly, in anembodiment of the invention the apparatus of the present inventioncomprises a TSLP package. A suitable TSLP package is available fromInfineon Technologies, Munich, Germany. The height of the package is 0.4mm, width 1.5 mm and length 2.3 mm.

The electronic apparatus of the present invention may be used in otherfrequency ranges and is not limited to the range from about 76 to 81 GHzas described.

FIG. 8 shows another embodiment of the present invention using a ThinSmall Leadless Package (TSLP). In order to connect the package 40 to aprinted circuit board (not shown) the package 40 comprises landinterconnects 85. The antenna chip 20 is directly connected to thecontact lands 85 using wirebonds 125.

FIG. 9 shows a typical, simplified block diagram of a monostatic FMCWradar sensor. A VCO 910, which can be connected to an external PLL via aprescaler 920 and the tuning input 930, generates the frequency ramps. Abuffer amplifier 940 amplifies the VCO output signal and isolates theVCO from the rest of the circuit. The amplified signal is fed to adirectional coupler 950 that feeds a part of the signal to the antenna970 where it is radiated and another part to the LO input of the mixer960. The incoming signal is fed from the antenna 970 to the coupler 950,where a part is fed to the RF input of the mixer 960 where it isdemodulated. In a simpler implementation, the transmit receive block 980can also be a diode.

FIG. 10 shows a typical, simplified block diagram of a data transmitter.A VCO 1010, which can be connected to an external PLL via a prescaler1020 and the tuning input 1030, generates the LO signal. A bufferamplifier 1040 amplifies the VCO output signal and isolates the VCO fromthe rest of the circuit. Via an optional filter 1050, the LO signal isfed to the LO input to an up-conversion mixer 1060, where the LO signalis modulated with a data signal 1100. After filtering with a filter 1070and amplification 1080 the RF signal is fed to the antenna, where it isradiated.

FIG. 11 shows a typical, simplified block diagram of a data receiver. AVCO 1110, which can be connected to an external PLL via a prescaler 1120and the tuning input 1130, generates the LO signal. A buffer amplifier1140 amplifies the VCO output signal and isolates the VCO from the restof the circuit. Via an optional filter 1150, the LO signal is fed to theLO input to a down-conversion mixer 1160, where the via antenna 1190,filter 1180 and LNA 1170 incoming signal is demodulated.

A combination of FIG. 10 and FIG. 11 on one common chip is alsopossible. This can be done with two individual antennas located atopposite sides of the chip or by one common antenna which is connectedby a switch or a duplex filter to the transmit and receive block.

FIG. 12 shows a further embodiment of the present invention. FIG. 12shows an electronic apparatus 10 having an antenna chip 20 with asubstrate 25 and an antenna structure 30. The antenna chip 20 isintegrated or packaged in a package 40 having a conducting chip mountingsurface 50 for mounting the antenna chip, and an encapsulating material60. Below the antenna structure 30 a first void 100 is arranged in thesubstrate 25. In order to provide additional mechanical stability to theantenna structure 30, the antenna structure 30 is supported by amembrane 35 which separates the antenna structure 30 from the first void100 in the substrate 25. Preferably, the membrane is made ofnon-conducting material, for example silicon oxide or silicon nitride.The membrane 35 may also comprises several layers of the same ordifferent materials.

The electronic apparatus shown in FIG. 12 further comprises a secondvoid 110 disposed between the antenna structure 30 and the encapsulatingmaterial 60. The second void 110 is provided by an additional cap 70that is placed on the antenna structure 30 before the packaging of theapparatus, i.e. prior to the application of the mold mass 60. A suitablecap for this purpose is for example a SU8 frame that has been providedwith conducting inner surface 75 to reflect the radiation emitted fromthe antenna structure 30. The height of the cap 70 may be adjusted tothe individual operating wavelength. Preferably, height of the cap 70 isa quarter of the operating wavelength to support radiation in thedirection of the back side of the antenna chip.

In order to allow the radiation to be emitted in the direction of theback side of the antenna chip the chip mounting surface 50 comprisesopenings 55 adjacent to the void 100 in the antenna substrate 25. FIG.13 shows a corresponding sectional top view of the embodiment shown inFIG. 12. Thereby, antenna opening 55 a in lead frame is used to transmitradiation from the antenna structure whereas antenna opening 55 b in thelead frame is used to receive radiation.

In the embodiment of the invention shown in FIG. 12, the circuit 120 andthe antenna chip 20 are integrated on a single chip using a singlesubstrate, which can contribute to further miniaturize the electronicapparatus and to reduce production costs. Thereby, the circuit 120 ispreferably a SiGe circuit.

The package shown in FIG. 12 is a Thin Small Leadless Package (TSLP). Inorder to connect the package 40 to a printed circuit board (not shown)the package 40 comprises land interconnects 85. The antenna chip 20 isdirectly connected to the contact lands 85 using wirebonds 125.

It is to be understood that the exemplary electronic apparatus depictedin FIGS. 1-13 above can be constructed using various types of chipfabrication and packaging technologies, and that the invention is notlimited to any specific chip fabrication and packaging technologiesdiscussed herein.

What is claimed is:
 1. An apparatus, comprising: a chip comprising asemiconductor substrate and an antenna structure provided at a frontside of the chip; a chip package comprising an encapsulating material;and a void arranged in the semiconductor substrate below the antennastructure, wherein the apparatus is configured to provide radiation inthe direction of the front side of the chip.
 2. The apparatus of claim1, wherein a vertical projection of the void onto the antenna structurehas substantially the same largest diameter as the largest diameter ofthe antenna structure or a larger diameter than the largest diameter ofthe antenna structure.
 3. The apparatus of claim 1, wherein the largestdimension of the shape of the first void, as projected vertically on theantenna structure, is approximately ten percent larger than the largestdimension of the antenna
 4. The apparatus of claim 1, furthercomprising: a high frequency circuit that is integrated in the chip. 5.The apparatus of claim 1, wherein the antenna structure has a sizesmaller than 2 mm².
 6. The apparatus of claim 1, further comprising: achip package comprising an encapsulating material and a chip mountingstructure, wherein the chip is mounted with a backside to the chipmounting structure.
 7. The apparatus of claim 6, further comprising: ahigh frequency circuit chip, which is mounted to the chip mountingstructure.
 8. The apparatus of claim 6, further comprising: a furthervoid in the encapsulating material, wherein the antenna structure isarranged between the void and the further void.
 9. The apparatus ofclaim 8, further comprising: a cap covering the antenna structure at thefront side of the chip; and a further void disposed between the antennastructure and the cap; wherein the antenna structure is arranged betweenthe void and the further void.
 10. The apparatus of claim 8, wherein theencapsulation material has a form of an encapsulating lid that is not indirect contact with the antenna chip to form the further void is formed.11. An apparatus comprising: a chip comprising a semiconductor substrateand an antenna structure provided on a front side of the chip; a chippackage comprising an encapsulating material and a chip mountingstructure, wherein the chip is mounted with a backside to the chipmounting structure; a void in the semiconductor substrate; and a furthervoid in the encapsulating material, wherein the antenna structure isarranged between the void and the further void, wherein the apparatus isconfigured to provide radiation in the direction of the back side of thechip.
 12. The apparatus of claim 11, further comprising: a cap that isplaced on the antenna structure at the front side of the chip, the caphaving a conducting inner surface to reflect radiation emitted from theantenna structure.
 13. The apparatus of claim 12, wherein the cap has aheight that is a quarter of an operating wavelength of the radiationemitted from the antenna structure.
 14. The apparatus of claim 11,wherein the chip mounting structure comprises at least one openingadjacent to the void in the semiconductor substrate to allow radiationbeing emitted in the direction of the back side of the chip.
 15. Theapparatus of claim 11, wherein the chip package further comprising alead frame, which forms the chip mounting structure.
 16. The apparatusof claim 11, further comprising: a high frequency circuit that isintegrated in the chip.
 17. The apparatus of claim 11, furthercomprising: a high frequency circuit chip, which is mounted to the chipmounting structure.